Ptc device

ABSTRACT

The present invention relates to a new PTC device having a configuration with which protrusion of solder paste and/or an excess portion of epoxy resin do not adversely affect a jig. Such PTC device  30  comprises a PTC member  32  and leads  34  and  36  electrically connected to both sides of the PTC member the PTC member comprises a PTC element 38 and metal electrodes  40  and  42  placed on both sides of the PTC element respectively, each lead is electrically connected to the metal electrode respectively via an electrically conductive connection portion  50 , and at least one  36  of the leads has a concave portion which is defined with a bottom portion  44  located adjacently to the metal electrode of the PTC member and a wall portion  46  surrounding the electrically conductive connection portion which connects the leads to the metal electrode.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/115,080, filed Jun. 12, 2014, which claims priorities to and thebenefit of Japanese Patent Application No. 2011-103107, filed on May 2,2011 and titled as “PTC device”, and Japanese Patent Application No.2011-197370, filed on Sep. 9, 2011 and titled as “PTC device”, theentire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a PTC device which comprises a PTC(Positive Temperature Coefficient) member and leads which are connectedto the both sides of the PTC member. In particular, the presentinvention relates to a PTC device which comprises a PTC member having alaminar polymer PTC element and metal electrodes placed on the bothsides of the PTC element as well as leads which are electricallyconnected to the metal electrodes respectively.

BACKGROUND ART

The above described PTC device is widely used as a protection devicewhich protects an electric element (such as a secondary cell)constructing various electric apparatuses or a circuit constructing suchelectric apparatuses when an excessive amount of current passes throughthe apparatuses. Also, the PTC device is widely used as a protectiondevice which interrupts a current flow through the apparatus when suchelectric element fails so that its temperature rises abnormally.

One example of such PTC device is shown in a schematic cross-sectionalview in FIG. 1. A PTC device 10 comprises a PTC member 12 and leads 14and 16 which are placed on the both sides of the PTC member. Theillustrated PTC device 10 is located in, for example, a charge/dischargecircuit of a secondary cell, and used as a circuit protection device tointerrupt an excess current when such current passes through thecircuit. In the illustrated embodiment, the lead 14 is electricallyconnected to a substrate which has a circuit protection circuit, whilethe lead 16 is electrically connected to a secondary cell side.

The PTC member 12 is composed of a PTC element 18 formed of anelectrically conductive PTC composition and metal electrodes 20 and 22which are placed on the both sides of the PTC element, and they aregenerally integrated by means of heat pressing.

The metal electrode 20 of the PTC member 12 is electrically connected tothe substrate side lead 14 with solder paste which is sandwiched by themetal electrode 20 and the lead 14, and the metal electrode 22 iselectrically connected to the cell side lead 16 via solder paste 24which is sandwiched by the metal electrode 22 and the lead 16.

In order to produce such PTC device, the following is carried out forexample: The solder paste 24 is placed on the substrate side lead 14,the PTC member 12 is place such that the metal electrode 20 is locatedon the solder paste 24, the solder paste 24 is place on the metalelectrode 22, and the cell side lead 16 is placed on the solder paste sothat an assembly of these members is formed. Thus formed assembly ispasses through a reflow furnace so as to melt the solder paste followedby solidifying the molten solder paste by cooling, whereby the PTCdevice is obtained. In order that the assembly is passed through thereflow furnace, a jig having a plurality of concave portions is used.Each of the concave portions of the jig can receive and keep all themembers superimposed in the above described order which form theassembly. The jig having a plurality of the assemblies formed bysuperimposing all the members in the concave portions is passed throughthe reflow furnace.

Such assemblies are passed through the reflow furnace to connect themembers together via the solder, so that the PTC devices are obtained.Then, an oxygen barrier layer 26 is formed on the side of the PTCmember. For such purpose, the obtained device is kept in other jig andan epoxy resin is applied onto the side of the PTC device to from acoating layer, followed by curing the layer to form the oxygen barriercoating 26.

PRIOR ART REFERENCE Patent Reference Patent Reference 1: InternationalPublication No. W02007/052790 SUMMARY OF THE INVENTION Problem to beSolved by the Invention

As to the above described connecting process, the assembly formed withthe PTC member and the leads which are placed on the both sides of thePTC member via solder paste is located in the jig which keeps theassembly as it is, and such assembly is supplied to the reflow furnace.In the reflow furnace, the solder paste placed between the metalelectrode and the lead is melted, and a portion of the solder pasteprotrudes out from between them and solidifies with being sandwichedbetween the assembly and a jig wall (In FIG. 1, the solder paste 28which solidifies with protruding is schematically shown). As a result,it may become difficult to take the PTC device out of the jig. Inaddition, since a portion of the solder paste in a solid conditionadheres to and remains in the jig. As a result, a need to clean the jigarises. Due to such matters, there is raised a problem of productionefficiency reduction of the PTC device.

When the oxygen barrier layer 26 is formed, a similar problem is raised.That is, an excess amount of an epoxy resin located between the jig walland a PTC device side is cured with adhering the jig wall. In this case,a need to clean the jig also arises. Due to such matters, there israised a problem of production efficiency reduction of the PTC device.

Since the PTC device is used widely as a protection element as describedabove, it is required to produce the PTC device as efficiently aspossible. Therefore, a problem to be solved by the present invention isto provide a new PTC device which solves at least one of the abovementioned problems as to the production of the PTC device. In otherwords, it resides in providing a new PTC device which has a structurewith which the protrusion of the solder paste and/or the excess portionof the epoxy resin as described above does not affect the jig.

Means to Solve the Problem

The present inventor has carried out extensive studies as to theprotrusion of the solder paste and the excess portion of the epoxy resinas well as the structure of the PTC device, and found that the abovementioned problem is solved by forming a PTC device by using a leadhaving a structure in which a portion of the lead is located between theprotruding solder paste and the jig wall, thus, achieved the presentinvention.

Thus, in the first aspect, the present invention provides a PTC devicewhich comprises a PTC member and leads electrically connected to bothsides of the PTC member, characterized in that the PTC member comprisesa PTC element (preferably, a laminar PTC member) and metal electrodes(preferably, metal foil electrodes) placed on both sides of the PTCelement respectively, each lead is electrically connected to the metalelectrode respectively via an electrically conductive connectionportion, and at least one of the leads has a concave portion which isdefined with a bottom portion located adjacently to the metal electrodeof the PTC member and a wall portion surrounding the electricallyconductive connection portion which connects the lead to the metalelectrode.

In a preferable embodiment, the PTC device according to the presentinvention, an exposed side portion of the PTC element which constructsthe PTC member is covered with an oxygen barrier layer.

As the lead which has the concave portion as described above, forexample the following may be used: a drawing processed lead which hasbeen formed to have a depression portion by processing at least aportion of a flat metal plate with drawing processing; or a pressingprocessed lead which has been formed to have a depression portion bypressing at least a portion of a flat metal plate.

When the lead having the concave portion as described above is used, thewall portion which defines the concave portion, namely a portion whichrises from the bottom portion and transversely (for example, vertically)with respect to the bottom portion, is located between a wall portion ofa jig which is used in producing the PTC device and the PTC member. As aresult, even though the solder paste protrudes from between the PTCmember and the lead by being heated in the reflow furnace, theprotruding solder paste portion contacts only the wall portion whichdefines the concave potion. Since the wall portion is located betweenthe protruding solder paste portion and the jig, the protruding solderpaste portion is prevented from further spreading outward to directlycontact with the wall of the jig In addition, also when the oxygenbarrier layer is formed, the wall portion of the concave portion islocated between the wall of the jig and a side portion of the PTCdevice, particularly a side portion of the PTC device which portion isnearer to the lead, so that the likelihood of a portion of the epoxyresin to directly contact with the wall of the jig is greatly reduced.

In the second aspect, the present invention also provides variouselectric apparatuses such as a secondary cell which comprise the PTCdevice described above and below.

Effect of the Invention

In the PTC device according to the present invention, since the leadhaving the concave portion is used, the protruding portion of the solderpaste which appears upon the production of the PTC device is notsubstantially contacted with the wall of the jig for the production. Asa result, the problem that the PTC device is not readily taken out ofthe jig, or the requirement that jig is cleaned so as to remove theprotruding solder paste which adhering to the jig is substantiallyeliminated. As a result, the PTC device can be produced efficiently,which improves the productivity of the PTC device. In addition, when theoxygen barrier layer is formed, since contact of a portion of the epoxyresin with the jig wall is prevented as much as possible, the likelihoodthat an excess amount of the epoxy resin adheres to the jig is greatlyreduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows a configuration of the prior art PTC devicein its cross-sectional view.

FIG. 2 schematically shows a configuration of one embodiment of a PTCdevice according to the present invention in its cross-sectional view.

FIG. 3 schematically shows a configuration of other embodiment of a

PTC device according to the present invention in its cross-sectionalview.

FIG. 4 schematically shows a lead of the PTC device shown in FIG. 2 in aperspective view while it is inverted upside down from the conditionshown in FIG. 2.

FIG. 5 schematically shows a jig 64 in a perspective view which is usedin the production of the PTC device.

FIG. 6 schematically shows a configuration of one embodiment of a PTCdevice according to the present invention in its cross-sectional view.

FIG. 7 schematically shows a side cross-sectional view of the PTC deviceshown in FIG. 6 for the purpose of easy understanding of the shape of anL-shaped lead.

FIG. 8 schematically shows a configuration of one embodiment of a PTCdevice according to the present invention in its cross-sectional view.

FIG. 9 schematically shows a side cross-sectional view of the PTC deviceshown in FIG. 8 for the purpose of easy understanding of the form of theL-shaped lead in the same way as FIG. 7.

EMBODIMENTS TO CARRY OUT THE INVENTION

Next, the PTC device according to the present invention will beexplained in detail with reference to the accompanied drawings. Aconfiguration of one embodiment of the PTC device according to thepresent invention is schematically shown in its cross-sectional view inFIG. 2 wherein one of the two leads has a concave portion. Theillustrated PTC device can be used, for example, as a circuit protectiondevice for a secondary cell.

The PTC device 30 comprises a PTC member 32 and leads 34 and 36 whichare electrically connected to the both sides of the PTC memberrespectively. In the illustrated embodiment, one lead 34 is, forexample, a substrate side lead which is connected to a circuit board,and the other lead 36 is, for example, a cell side lead which isconnected to a secondary cell. Similarly, to the embodiment shown inFIG. 1, the PTC member 32 comprises a PTC element 38 in the form of alayer which is made of an electrically conductive PTC composition aswell as metal electrodes 40 and 42 which are placed on the both sides ofthe PTC element respectively.

The metal electrodes 40 and 42 are adjacent to the leads 34 and 36,respectively, and they are electrically connected with each other byelectrically conductive connection portions 50 between them. Thiselectrically conductive connection portion may be any appropriateconnection as long as it electrically connects between the electrode andthe lead. For example, it represents a connection portion which isformed by a general material which is used for electrically connectingin the production of an electric apparatus, such as a solder, a solderpaste (for example, a solder in which an epoxy resin is used as a flux),an electrically conductive adhesive or the like.

In the illustrated embodiment, the cell side lead 36 of the PTC device30 comprises a bottom portion 44 which is located adjacently to themetal electrode 42 of the PTC member and a wall portion 46 whichsurrounds a side portion of the electrically conductive connectionportion which connects the lead 36 to the metal electrode 42, and thebottom portion 44 and the wall portion 46 define the concave portion. InFIG. 4, a perspective view of the lead 36 of the PTC device shown inFIG. 2 is schematically shown while inverting the lead upside down fromthe condition shown in FIG. 2. As illustrated, the lead 36 has the wallportion 46 which protrude upward from a periphery of the bottom portion44, thereby the concave portion 48 which opens upwardly is defined. Itis noted that a thickness of the bottom portion 44 and a height of thewall portion 46 can be appropriately selected depending on theapplication of the lead 36. In FIG. 4, the thickness and the height ofthe lead are not the same as those in FIG. 3. In the embodiment shown inFIG. 4, the lead 36 as a whole has the concave potion 48, but in otherembodiment, the lead may be a plate-form lead a portion of which has aconcave portion 48. It is noted that as the lead 36, a lead which isobtained, for example, by subjecting a metal plate having a thickness offor example 0.15 mm to 0.5 mm to a drawing process. In this case, thethickness of the bottom portion 44 which defines the concave portion 48is, for example, about 0.13 mm to 0.48 mm. Generally, the thickness ofthe bottom portion 44 is more preferably 0.25 mm to 0.43 mm, andparticularly preferably 0.37 mm to 0.39 mm.

In the PTC device, the lead 36, particularly its bottom portion 44 islocated adjacently to the metal electrode 42 of the PTC member, andthere is an electrically conductive connection 50 between them. That is,the lead 36 is electrically connected to the metal electrode 42 throughthe electrically conductive connection portion 50. The other lead 34 islocated adjacently to the metal electrode 40 of the PTC member, andthere is an electrically conductive connection portion 50 between them.That is, the lead 34 is electrically connected to the metal electrode 40via the electrically conductive connection portion 50. It is noted thatthe other lead 34 may have portions 35 which extend outward from theboth end sides of the lead 34 (therefore, outward from and below theboth end sides of the lead 36) as shown with broken lines in FIG. 2. Ina further embodiment, only one end side may have a portion which extendsoutward from the end side of the lead 34 shown with a solid line. In theembodiments in which the lead 34 extends outward, this extending portionmay be used for welding the PTC device according to the presentinvention to other electric element (such as an electric apparatus, alead, a pad or the like).

In the illustrated embodiment, the wall portion 46 of the lead 36surrounds a side of the electrically conductive connection portion 50which connects the lead 36 to the metal electrode 42. In the illustratedembodiment, the wall portion 46 additionally surrounds a side of themetal electrode 42 and a side of an upper portion of the PTC element 38in addition to the side of the electrically conductive connectionportion 50. Such additionally surrounding is particularly preferable,but surrounding at least the side of the electrically conductiveconnection portion 50 is preferable.

When the PTC device shown in FIG. 2 is produced, for example a jig 64having a concave portion 62 on a plate 60 as shown in FIG. 5 is used.The lead 36 is first placed on a bottom portion 66 of the concaveportion 62 of the jig, and a solder paste (namely, corresponding to aprecursor of the electrically conductive connection portion) 50 issupplied onto the lead 36. The PTC member 32 is placed on the solderpaste, other solder paste 50 is supplied onto the metal electrode 40 ofthe PTC member, and finally the substrate side lead 34 is placed on thesolder paste so that an assembly of these members is formed within theconcave portion 62 of the jig 64. Preferably, the assembly and theconcave portion of the jig are constructed such that thus formedassembly fills substantially a whole of the space within the concaveportion 62 of the jig 64 (that is, such that the assembly is just fittedinto the concave portion of the jig). The jig 64 having the assembly inits concave portions 62 is heated in a reflow furnace so as to melt thesolder paste followed by solidifying, thereby the PTC device is obtainedwherein the assembly is bonded together. It is noted that portions 52and 54 are schematically shown in FIG. 2 wherein the portions are formedwith a portion of molten solder paste which protruded out followed bysolidifying.

As readily seen, the protruding portion 52 cannot move any more outwardon the side of the lead 36 by means of the wall portion 46, so that itdoes not spread out outward excessively. Therefore, the protrudingportion 52 does not adhere to the wall portion 68 which defines theconcave portion 62 as a cavity of the jig. Therefore, effects areprovided, which solve the problem of difficulty of removing the PTCdevice from the jig due to the protruding portion 52, and also theproblem of requirement of cleaning of the jig induced by the adhesion ofthe solder paste to the wall portion 68.

On the other hand, since the lead 34 does not have a wall portion, thereis a likelihood in which the protruding portion 54 spreads furtheroutward. In that case, the protruding portion may adhere to the wallportion 68 which defines the cavity 62 of the jig 64 depending on anamount of the solder paste, a heating condition and the like if itspreads excessively outward. In this case, it becomes difficult to takethe PTC device out of the jig. In addition, the solder paste remainsadhering to the wall portion 68, and therefore the jig cleaning becomesrequired.

It is noted that in the illustrated embodiment, the wall portion 68 ofthe concave portion which the jig 64 defines may not necessarily bepresent over a whole periphery of the concave potion 62, and the wallportion may be a portion of a wall which is present over the wholeperiphery of the concave potion, for example, the wall portion 68 may bepresent at only four corners of the concave portion.

The PTC device shown in FIG. 2 further comprises an oxygen barrier layer47 on the side of the PTC member. The oxygen barrier layer 47 is presentat least on the side of the PTC element 38, and prevents an electricallyconductive filler (for example, nickel filler) contained in the PTCelement from being oxidized. When the oxidation of the electricallyconductive filler does not have to be cared, for example, in the casewherein carbon filler is used, no oxygen barrier layer has to beprovided.

When the oxygen barrier layer is provided, an epoxy resin is supplied toa side of an assembly of which connection has been done in the reflowfurnace as described above with keeping such assembly in an appropriatejig, followed by solidifying (or curing) the epoxy resin so as to formthe oxygen barrier layer 47. As seen from FIG. 2, when the epoxy resinis supplied to the side of the assembly, the epoxy resin is preventedfrom overflowing to the outside by the wall portion 46 of the lead 36even though an amount of the supplied resin is excessively large.Therefore, the adhesion of the outflowed epoxy resin to the jig isprevented. Therefore, an effect is provided, which frequency of cleaningof the jig due to the adhering of the epoxy resin is greatly reduced.

Similarly to FIG. 2, other embodiment of the PTC device 30′ according tothe present invention is schematically shown in FIG. 3. The illustratedembodiment is substantially the same as the embodiment shown in FIG. 2except that the cell side lead 34′ also has a concave portion which isdefined by a bottom portion 44′ which is located adjacently to the metalelectrode 40 of the PTC member 32 and a wall portion 46′ which surroundsa periphery of a side of the electrically conductive connection portion50 which connects the lead to the metal electrode. In the PTC device 30′shown in FIG. 3, since the substrate side lead also has the wall portion46′, the effects which are provided by having wall portion 46 aresimilarly provided by the wall portion 46′ of the substrate side lead34′. It is noted that, as seen from FIG. 3, the oxygen barrier layer 47′is provided with being prevented from outflowing to outside of the PTCdevice 30′.

Similarly to FIG. 2, one of preferable embodiments of the PTC deviceaccording to the present invention is shown in FIG. 6 as a schematiccross-sectional view. In the illustrated embodiment, the PTC device 100comprises a PTC member 102 and leads 104 and 106 which are electricallyconnected to the both sides of the PTC member. It is noted that the PTCmember 102 comprises a PTC element and metal electrodes (preferablymetal foil electrodes) which are placed on the both sides of the PTCelement similarly to the above described embodiments, but these areshown in an integrated manner as the PTC member 102.

One lead 106 provided on the lower side of the PTC member 102 is a leadhaving a concave portion similarly to the above described cell side lead36, and it may be, for example, a drawing processed lead. The other lead104 provided on the upper side of the PTC member 102 is a lead which isalso a so-called an L-shaped lead. An oxygen barrier layer 112 isprovided around the PTC member 102 sandwiched by such leads similarly tothe embodiment of FIG. 2 or FIG. 3, so that an exposed side surface ofthe PTC member is covered by the barrier layer.

The L-shaped lead has a character L shape when the lead is watched fromits side, and a horizontal portion 108 of the L-shaped lead iselectrically connected to the metal electrode on the upper side of thePTC member 102. Such connection may be carried out in any appropriatemanner as long as both of electric connection and bond to the PTC memberare achieved. For example, welding (for example, resistance welding),soldering, connecting with an electrically conductive adhesive or anelectrically conductive paste or the like may be employed. It is notedthat the L-shaped lead 104 has a vertical portion 110 of the L-shapedlead which forms an angle of 90 degrees with respect to the horizontalportion 108, and these portions together form the L-shaped lead 104.

By providing such L-shaped lead as described above, when the PTC deviceis electrically connected to other electric element (for example, awiring on a substrate, a pad, a land, an element, other lead or thelike) is formed, an electric connection may be formed between thevertical portion 110 and the other electric element. Therefore, hightemperature heat applied when the electric connection is formed (forexample, heat by means of heating upon connecting with soldering,welding, an electrically conductive adhesive or the like) is supplied tothe vertical portion 110 and it is not directly supplied to thehorizontal portion 108.

As a result, the high temperature heat supplied to the vertical portionis also transferred to the horizontal portion 108 with dissipating tovarious directions. That is, an amount of heat which is transferred tothe horizontal portion 108 is reduced, and temperatures of thehorizontal portion 108, and thus the PTC member 102 located under theportion 108 and the electrically conductive connection portion (notshown in FIG. 7, a portion corresponding to the portion 50 in FIG. 2),and the oxygen barrier layer (if any) are not so raised to a temperatureof the vertical portion. Thereby, it is convenient that transferring ahigh temperature applied to the PTC member, particularly to the PTCelement when the PTC device is connected to the electric element can besuppressed.

For readily understanding the shape of the L-shaped lead, it is notedthat a cross-sectional view of the PTC device is schematically shown inFIG. 7 when the PTC device is watched in a direction along an arrow A asshown in FIG. 6 (corresponding to a schematically side end elevationview of the PTC device in FIG. 6). As seen easily, the L-shaped lead hasthe horizontal portion 108 and the vertical portion 110, and the angle awhich is formed by those portions is substantially goo in theillustrated embodiment. However, this angle a may be any appropriateangle. For example, it may be 45° to 135°. It is preferably 60° to 120°, and more preferably 80° to 100° , and most preferably goo. In thesense of allowing such angle ranges, it may be practical that a“non-horizontal portion” is used in place of the “vertical portion”.

A further preferable embodiment of the PTC device according to thepresent invention which comprises an L-shaped lead is shown in FIG. 8similarly to FIG. 6. In this embodiment, the PTC device 114 comprises alead 116 having a concave portion via an electrically conductiveconnection (not shown) on a PTC member 118. This lead 116 is similar tothat explained before, and it is, for example, a drawing processed lead.In the illustrated embodiment, an L-shaped lead 120 which issubstantially similar to the above described L-shaped lead iselectrically connected onto the lead 116. The connection between thoseleads may be carried out in any appropriate manner. For example,welding, soldering, connecting with an electrically conductive adhesiveor the like may be used for carrying out connecting. It is noted that inthe illustrated embodiment, the lead 116 and the lead 120 which areseparate members are connected together, but those leads may beoriginally an integrated single member. For example, an L-shaped leadhaving a concave portion may be formed by pressing or drawing a metalsheet for producing a lead to form a wall portion 122 and a bottomportion 124 of the concave portion on a portion of the sheet, andfolding, with respect to said portion including the concave portion ofthe sheet, the other portion of the metal sheet. In this case, theportion which includes the concave portion corresponds to the horizontalportion (116+120), and the other portion which is folded corresponds tothe vertical portion or the non-horizontal portion 126. It is noted thatthe lead 125 on the lower side of the PTC member 118 is shown as aconventional flat lead in the illustrated embodiment.

In the PTC device according to the present invention, since the leadhaving the concave portion is used, the problem as to the solder pasteprotrusion can be suppressed as described above. As shown in FIG. 6 andFIG. 8, when one of the leads of the PTC device is the L-shaped lead,high temperature which would be applied to the lead 36 corresponding tothe horizontal portion if the PTC device as shown in FIG. 2 or FIG. 3 isused is prevented from being directly conducted to the PTC member andits surroundings when the PTC device is connected to other electricelement. As a result, adverse effects of the high temperature can besuppressed which are provided to the PTC element as well as the oxygenbarrier layer 112 and the electrically conductive connection portion(not shown in FIG. 7, a portion corresponding to the portion 50 in FIG.2) around the PTC element.

For example, in the PTC device as shown in FIG. 6 or FIG. 8, even whenhigh temperature is applied to the vertical portion 110 or 126, apossibility that the high temperature is transferred to the electricallyconductive connection portion, and solder therein is re-melted andprotrudes out can be reduced. In addition, even though a small amount ofsolder protrudes out, it is advantageous in that the protruded soldermay be prevented from getting over the wall portion 122 which forms theconcave portion by using the L-shaped lead as a lead having the concaveportion. It is noted that in the illustrated embodiment with theL-shaped lead, one lead which is provided on the PTC member is theL-shaped lead, while the both of the leads on the PTC member may be theL-shaped leads when necessary, and also only one lead may have theconcave portion, while each of the leads may have the concave portion.

As readily seen, the above mentioned advantage is provided by using theL-shaped lead and combining it with the lead having the concave portionaccording to the present invention. Even though the L-shaped lead isused and is combined with a PTC device in which no lead having theconcave portion is used, it is advantage in that the high temperatureeffect can be avoided as much as possible. In addition, by employing theL-shaped form, since an area occupied by the lead can be smaller, thereis an advantage in that a size of an electric or electronic apparatus inwhich the PTC device is comprised can be compact.

Further, by folding the vertical portion 110 and placing it on thehorizontal portion 108 after the PTC device, for example, the right sideof the vertical portion 110 is connected to the other electric element,other electric element can be located over the PTC device, and this isadvantage in that the electric or electronic apparatus can be compact.

As readily seen, the advantage of moderating the adverse effect which isprovided by the high temperature when the PTC device is connected to theother electric element can be enjoyed by using the L-shaped lead for thelead in any PTC device having a lead.

Therefore, in the third aspect, the present invention provides a new PTCdevice comprising a PTC member and a lead which is electricallyconnected to at least one of main surfaces of both sides of the PTCmember (i.e. a lead which is electrically connected to one main surfaceof the PTC member, or two leads each of which is electrically connectedto each of main surfaces, respectively), characterized in that the PTCmember comprises a PTC element (preferably, a laminar PTC element) andmetal electrodes (preferably, metal foil electrodes) placed on bothsides of the PTC element, the lead is electrically connected to eachmetal electrode of the PTC member via an electrically conductiveconnection, and at least one lead is the above mentioned L-shaped lead.

In the broadest meaning of the PTC device according to the third aspect,features other than the L-shaped lead provided on at least one of themain surfaces of the PTC member is not particularly limited. In thissense, in the PTC device of the third aspect, the PTC member may be ofany appropriate kind, for example, no lead is provided on the other mainsurface of the PTC member, and the metal electrode placed on the PTCelement may be exposed.

In other embodiment of the PTC device of the third aspect, the mainsurfaces of the both sides of the PTC member have the leads, in thiscase, the L-shaped lead is provided on one surface while a flat lead isprovided on the other surface. In other words, the PTC device of thisembodiment comprises the PTC member and the leads provided on its bothsides, and at least one lead is the L-shaped lead or comprises theL-shaped lead. The term “comprises the L-shaped lead” corresponds to anembodiment wherein the L-shaped lead is bonded to a flat lead so thatthey form an integrated lead as described below.

In the above mentioned PTC device of the third aspect, the features ofthe PTC device of the above mentioned first aspect according to thepresent invention are applicable excepting a feature that the PTC membercomprises a lead on at least one of the main surfaces and a feature thatsuch lead is the L-shaped lead. Therefore, since for example, the PTCmember, the oxygen barrier layer, the electrically conductive connectionportion and the like are already known, their explanations are omitted.

As to the above mentioned PTC device of the third aspect, in onepreferable embodiment, a surface which is exposed because of noprovision of a lead is covered by the above mentioned oxygen barrierlayer. However, in the PTC device of the third aspect, when oxidation ofan electrically conductive filler contained in the PTC element is not aproblem or negligible, the oxygen barrier layer may be excluded. Forexample, when carbon black or TiC is used as the electrically conductivefiller, the oxygen barrier layer may be omitted.

As to the above mentioned PTC device of the third aspect, in a furtherpreferable embodiment, at least one lead may be the above mentioned leadhaving the concave portion, and the L-shaped lead may be integrated withthe lead having the concave portion or may be an L-shaped lead which isconnected (or bonded) to the lead having the concave portion placed onthe PTC member. Therefore, the both of the leads may those which havethe concave portions. In a further preferable embodiment of the PTCdevice of the third aspect, the both of the leads provided on the bothside of the PTC member may be the L-shaped leads.

The L-shaped lead which the PTC device of the third aspect as describedabove is preferably formed such that a surface which defines thehorizontal portion and a surface which defines the vertical portion forma specific angle a as described above, and it is also preferable thatthe vertical portion can be folded onto the horizontal portion. It isnoted that the L-shaped lead may basically be a structure which isformed by folding a rectangular sheet to form a specific angle (forexample,) 90°, and it may have a cutout portion 128 which makes foldingto form the L-shape and folding after connecting to the other electricelement easy, and the cutout portion may be provided at any appropriatelocation on a border area (for example, both ends of the border area, orin-between them) between the horizontal portion and the vertical portionas shown.

EXPLANATION OF THE REFERENCE NUMERALS

-   10—PTC device, 12—PTC member,-   14—substrate side lead, 16—cell side lead,-   18—PTC element, 20—metal electrode,-   22—metal electrode,-   24—electrically conductive connection,-   26—oxygen barrier layer, 28—protruding portion,-   30—PTC device, 32—PTC member,-   34—substrate side lead, 35—extending portion,-   36—cell side lead, 38—PTC element,-   40—metal electrode, 42—metal electrode,-   44—bottom portion, 46—wall portion,-   47, 47′ oxygen barrier layer, 48—concave portion,-   50—electrically conductive connection portion, 52—protruding    portion, 54—protruding portion,-   60—plate, 62—concave portion,-   64—assembly forming jig, 66—bottom portion,-   68—wall portion, 100—PTC device, 102—PTC element,-   104—lead, 106—lead, 108—horizontal portion,-   110—vertical portion (or non-horizontal portion),-   112—oxygen barrier layer, 114—PTC device,-   116—lead having a concave portion, 118—PTC member,-   120—L-shaped lead, 122—wall portion,-   124—bottom portion, 125—bottom side lead,-   126—vertical portion (or non-horizontal portion),-   128—cutout portion.

What is claimed is:
 1. A positive temperature coefficient (PTC) devicecomprising: a PTC member comprising a PTC element, a first metalelectrode disposed on a first side of the PTC element, and a secondmetal electrode disposed on a second side of the PTC element oppositethe first side; and a first lead electrically connected to the firstmetal electrode via a first electrically conductive portion and a secondlead electrically connected to the second metal electrode via a secondelectrically conductive portion; wherein the first lead has a concaveportion defined by a bottom portion located adjacent the first metalelectrode and a wall portion surrounding the first electricallyconductive portion.
 2. The PTC device of claim 1, wherein the secondlead has a concave portion defined by a bottom portion located adjacentthe second metal electrode and a wall portion surrounding the secondelectrically conductive portion.
 3. The PTC device of claim 1, whereinthe wall portion surrounds a side of the first metal electrode.
 4. ThePTC device of claim 1, further comprising a third, L-shaped lead havinga first portion connected to the first lead in flat abutment therewithand a second portion extending away from the first portion at atransverse angle.
 5. The PTC device of claim 4, wherein the firstportion and the second portion form an angle in a range between 45degrees and 135 degrees.
 6. The PTC device of claim 4, wherein thesecond portion is configured to be folded from a first position in whichthe second portion is perpendicular to the first portion to a secondposition in which the second portion forms an angle of less than 45degrees with the first portion.
 7. The PTC device of claim 1, whereinthe first lead has a first portion that is in direct contact with thefirst electrically conductive portion and has a second portion that isnot in direct contact with the first electrically conductive portion,wherein the second portion is configured to be folded from a firstposition in which the second portion is perpendicular to the firstportion to a second position in which the second portion forms an angleof less than 45 degrees with the first portion.
 8. The PTC device ofclaim 7, wherein, in the first position, the first portion and thesecond portion form an angle in a range between 45 degrees and 135degrees.
 9. The PTC device of claim 1, wherein the second lead extendsoutward beyond a side of the PTC member for facilitating connection toanother circuit element.
 10. The PTC device of claim 1, furthercomprising an oxygen barrier disposed between the wall portion of thefirst lead and the PTC member.